The present invention relates to expansion bolts and, more specifically, to a sandwich type expansion bolt, which comprises two bolt halves with an insert block sandwiched in therebetween, and a nut threaded onto the bolt halves to secure the bolt halves to the hole of the object into which the bolt halves are inserted.
A regular expansion bolt, as shown in FIG. 1, comprises a socket 1, a screw bolt 2 threaded into the socket 1. The socket 1 has an internally threaded body 10, and a split 12 in the expanded rear end thereof. After insertion of the socket 1 into a hole in an object 3, the threaded shank 20 of the screw rod 2 is threaded into the internally threaded body 10 of the socket 1 to expand the split rear end of the socket 1, causing the socket 1 to be firmly secured to the object. This structure of expansion bolt can only support a small object that has less gravity weight. If the expansion bolt is used to support a heavy object, for example, a stone material on the outside wall of a building, the object may fall from the socket 1 and the screw bolt 2 to hit passers-by accidentally.
The present invention has been accomplished to provide a sandwich type expansion bolt, which eliminates the aforesaid problem. According to one aspect of the present invention, the expansion bolt comprises two symmetrical bolt halves, the bolt halves each having an inner side, and outer side, a front end, a rear end, and outer threads provided at the outer side for the mounting of a nut, an insert block inserted in between the bolt halves after the bolt halves have been attached together and inserted into a hole on an object, and a nut threaded onto the outer threads of the bolt halves to secure the bolt halves to the hole of the object into which the bolt halves are inserted. According to another aspect of the present invention, positioning means is provided to prevent the insert block from falling out of the bolt halves.